A candidate neural correlate of consciousness (NCC) in vision is the visual awareness negativity (VAN), an event-related potential occurring about 200 ms after stimulus onset over posterior electrode sites. Two preregistered experiments tested whether VAN is more sensitive to low-level detection awareness (seeing something) or high-level identification awareness (seeing what it is). In Experiment 1 (N = 30), using digits or letters, VAN was similarly sensitive to both types of awareness. In Experiment 2 (N = 28), stimulus size did not affect VAN for identification. Results confirm VAN's sensitivity to both detection and identification but suggest limited specificity in separating low-level from high-level experiences.
Electrophysiological recordings are commonly used to study the neural correlates of consciousness. Previous research is inconsistent as to whether awareness can be indexed with visual awareness negativity (VAN) at about 200 ms or if it occurs later. This preregistered study tested for VAN and whether stimulus size may account for inconsistent findings. Subjects viewed low-contrast Gabor patches in four visual quadrants; Gabor size (large and small) was varied and calibrated to each subject's threshold. Event-related potentials were derived from trials where subjects localized Gabors correctly, comparing trials with reported awareness versus no awareness. Bayesian analyses revealed very strong evidence for VAN for both sizes, but no evidence for or against an effect of stimulus size. The findings provide evidence for VAN as an early neural correlate of awareness.